In recent years, the demands of racers and recreational users alike for greater performance and maneuverability have driven the designers of personal watercraft to reconsider the control mechanisms traditionally used for steering, decelerating and trimming. In general, steering, decelerating and trimming can be achieved in a variety of manners, either independently of one another or synergistically.
Essentially, the steering of a boat can be achieved by either turning the source of propulsion, such as an outboard motor or a jet-boat nozzle, or by actuating the boat's control surfaces. These control surfaces can be substantially vertical such as the common rudder on a stern drive or they can be substantially horizontal, such as flaps and tabs. Examples of steering mechanisms involving vertical fins or rudders are found in U.S. Pat. Nos. 4,615,290 and 4,632,049, issued to Hall et al., and in U.S. Pat. No. 4,352,666, issued to McGowan. Examples of steering mechanisms involving horizontal tabs or flaps are found in Mardikian's U.S. Pat. No. 5,193,478.
Decelerating can generally be accomplished in one of three ways: by either reversing thrust, by redirecting the thrust toward the bow of the watercraft, or by creating drag by introducing a control surface substantially perpendicular to the watercraft's direction of travel. Decelerating by reversing thrust is perhaps the most common technique, simply requiring the propellor to turn backwards. The main problem associated with this technique is that decelerating is slow due to the time lag required to stop and then to reverse the propellor.
Redirecting the thrust toward the bow is a braking technique currently employed by numerous personal watercraft. Examples of thrust-reversing buckets or reverse gates have been disclosed by Kobayashi et al. in U.S. Pat. Nos. 5,062,815, 5,474,007, 5,607,332, 5,494,464 as well as by Nakase in U.S. Pat. No. 5,154,650. Although these thrust-reversing buckets direct the water jet backwards, they also have a propensity to direct the water jet downwards. This downward propulsion lifts the stern of the watercraft and causes the bow to dive. The sudden plunging of the bow not only makes the watercraft susceptible to flooding and instability but also makes it difficult for the rider to remain comfortably seated and firmly in control of the steering column.
Mardikian discloses in U.S. Pat. No. 5,092,260 a brake and control mechanism for personal watercraft involving a hinged, retractable flap mounted on each side of the hull capable of being angled into the water to slow the boat. However, when the actuator is extended, the flap pivots such that the trailing edge is lower than the leading edge, thereby creating an undesirable elevating force at the stern.
Trimming or stabilizing of a watercraft is normally achieved by adjusting the angle of the tabs mounted aft on the hull. Trim-tabs are used to alter the running attitude of the watercraft, to compensate for changes in weight distribution and to provide the hull with a larger surface for planing. Examples of trim-tab systems for watercraft are disclosed in Cluett's U.S. Pat. No. 4,854,259, Sasawaga's U.S. Pat. No. 4,961,396 and Schermerhorn's U.S. Pat. No. 4,323,027. Typically, these trim-tabs systems are actuated by electronic feedback control systems capable of sensing the boat's pitch and roll as well as wave conditions and then making appropriate adjustments to the trim-tabs to stabilize the boat. Examples of trim-tab control systems are found in Davis' U.S. Pat. No. 5,263,432, Ontolchik's U.S. Pat. No. 4,749,926, Atsumi's U.S. Pat. No. 4,759,732 and Takeuchi's U.S. Pat. No. 4,908,766. The foregoing trim-tab mechanisms deflect the water downward and thus elevate the stern. The stabilizing system for watercraft disclosed by O'Donnell in U.S. Pat. No. 4,967,682 attempts to address this problem by introducing a twin-tab mechanism capable of deflecting the flow of water under the hull either upwards or downwards to either elevate or lower the stern of the watercraft. O'Donnell's twin-tab mechanism, however, is designed expressly for stabilizing a watercraft and not for braking.
Steering, braking and trimming can also be performed synergistically. Mardikian's U.S. Pat. No. 5,193,478 discloses an adjustable brake and control flaps for steering, braking and trimming a watercraft. The flaps, located at the stern, in their fully declined position act as powerful brakes for the boat. Differential declination of the flaps results in trimming and steering of the boat. The flaps provide steering, braking and trimming in a manner analogous to the flaps and ailerons of an aircraft. During braking, however, the downward sweep of the tabs causes the stern to rise and the bow of the personal watercraft to plunge, often creating the potential for flooding and instability. Not only is the plunging of the bow uncomfortable for the rider but the watercraft is more difficult to control during hard braking maneuvers.
Finally, Korcak's U.S. Pat. No. 3,272,171 discloses a control and steering device for watercraft featuring a pair of vanes that can be pivotally opened below the hull of the watercraft to which they are mounted. The vanes are hinged at the ends closest to the stern and open toward the bow of the watercraft. As water is scooped by the opening vanes, the force of the water impinging on the vanes forces the vanes to open even more. In order to prevent the vanes from being violently flung open against the underside of the watercraft, a ducting system has been incorporated into the vanes to channel scooped water through the rear of the vanes to cushion the hull from the impact of the rear of the vanes. One of the shortcomings of this control mechanism, however, is that the scooping action of the vanes induces a great deal of turbulence on the underside of the watercraft especially when braking at high speeds. Secondly, the amount of water that is channeled through the ducts of the vanes is minimal and thus braking might, in some conditions, be too harsh. Thirdly, the presence of the vanes (even when full retracted) and their associated attachment bases on the underside of the watercraft create drag at high speeds. Fourthly, the vanes are not integrated with a main steering mechanism (such as a rudder or steerable nozzle) to provide better cornering. Fifthly, the vanes may scoop up seaweed, flotsam or other objects floating in the water that may prevent the vanes from closing or may clog the ducts in the vanes. Finally, to close the vanes when they are scooping water requires large gears whose weight causes the rear of the watercraft to sag.
Thus, there is a need for an improved watercraft control mechanism capable of steering and/or decelerating and/or trimming a watercraft without causing the stern to elevate and the bow to plunge.